Pneumatic timer and sequencer apparatus and system

- Docket No. DW-397 ~76921 SPECIFICATION .

PNEUMATIC TIMER AND SEQUENCER APPARATUS AND SYSTEM Field of Invention This invention concerns improvements in pneumatic timer and sequencer apparatus and systems.

The invention is particularly useful in applications where hostile operating environments are encountered.

Description of the Pxior Art The pneumatic timer and sequencer appara~us available in accordance with the prior art of which I am a~are were not compatible with the hostile operating environments that are encountered in many applications.

Such prior art apparatus would not function reliably in the presence of contaminants including dirt, water, oil, etc; or under severe vibration conditions and extremes of ambient temperature.

Further, such prior art apparatus was not susceptible to normally available and feasible field maintenance.

In addition, the timing cycles provided by such apparatus were not constant, but varied considerably in response to variations in the pressure of the pneumatic supply, The objective of the present invention is to provide pneumatic timer and sequencer apparatus that is significantly improved in the context of the problems and disadvantages above-mentioned.

117692~ Summary of the Invention The present invention provides, according to one aspect thereof, a cyclic event timing system including a timing actuator comprising: fluid cylinder means;

fluid piston means disposed in said cylinder means and dividing said cylinder means into first and second opposed fluid chambers, said piston means being reciprocable through a timing stroke and a retraction stroke, said piston means having first and second unbalanced effective fluid areas exposed to said first and second chambers, respectively, with the first fluid area being larger than the second fluid area and effective to urge said piston means in the direction of said timing stroke and the second fluid area being effective to urge said piston means on said retraction stroke;

conduit means in communication with a source of pressure fluid and with valve means operable to be in open and closed positions for delivering pressure fluid to means for performing a work function and for restricting flow of pressure fluid through said conduit means, respectively, said valve means being responsive to movement of said piston means on said timing stroke and said retraction stroke to be actuated to an open position and a closed position, respectively;

a first passageway in communication with said first chamber and said conduit means between said source and said valve means for conducting pressure fluid to act on said first fluid area, a second passageway in communication with said second chamber and with said conduit means between said source and the point of communication of said first passageway with said conduit means, said actuator being responsive to a predetermined pressure condition in said conduit means said first and second chambers to move said piston means on a timing stroke to open said valve means; and :., :,~,., ~ 2a- 1176921 first orifice means interposed in said conduit means between said first and second passageways and providing a resistance to fluid flow through said conduitmeans sufficient to provide for pressure fluid acting on said second fluid area to move said piston means on a retraction stroke to effect closing of said valvemeans, and the rate at which said piston means is acted on by pressure fluid to effect a timing stroke is controlled by the rate at which fluid flows through said first passageway to act on said first fluid area.

According to another aspect of the invention there is provided in a cycle timing system for controlling the flow of a pressure fluid wherein relatively large volumes of said fluid are released cyclically to perform a work function; a source of pressure fluid, a conduit connected to said source and to a valve operable to release timed flow of pressure fluid from said conduit toperform a work function, a cycle timing actuator including cylinder means, piston means disposed in said cylinder means and forming first and second opposed fluid chambers, first and second pressure surfaces on said piston means facing said first and second chambers, respectively, said first pressure surface havingan effective area less than said second pressure surface, said piston means being operably colmected to said valve for effecting opening and closing of saidvalve in response to movement of said piston means under the urging of pressure fluid acting on said piston means, first and second passage means in communication with said first and second chambers, respectively, and with said conduit, ~id first passage means providing relatively unrestricted fluid flow communication between said first chamber and said conduit, said second passage means being in communication with said conduit between the point of communication of said first passage means with said conduit and said valve, and a flow restriction interposed in one of said conduit and said second passage means at a point between -' -2b- ~76921 said point of communication of said first passage means with said conduit and said second chamber whereby said piston means is operable in response to pressure fluid flowing to said first and second chambers from said source when said valve is closed to move through a timing stroke to open said valve, and then through a retraction stroke to close said valve in response to changes in fluid pressures in said second chamber relative to said first chamber.

According to a further aspect of the invention there is provided a system for reverse air flow cleaning of a plurality of air filter elements including a plurality of pilot pressure fluid operated valves in communication with a source of pressure air by way of a conduit, a plurality of pilot control valves for providing a pressure fluid signal to respective ones of said fluid operated valves, and a cyclic timing actuator for sequentially actuating said pilot control valves to actuate said fluid operated valves, respectively, said actuator comprising:

cylinder means, piston means disposed in said cylinder means and dividing said cylinder means into first and second opposed fluid chambers, said piston means including first and second pressure surfaces of different effective areas and exposed to said first and second chambers, said piston means being operable to actuate a selected one of said pilot control valves in sequence during successive timing strokes of said piston means, first and second passageways in communication with said conduit and with said first and second chambers, respectively, between said source and said fluid operated valves, a flow restricting orifice interposed in said conduit between said first and second passageways and operable to provide a pressure differential between said first ~ -2c- ~76921 and second passageways in response to opening one of said fluid operated valves to effect a retraction stroke of said piston means, said piston means being operable to move through repeated cycles, each including a timing stroke and a retraction stroke for sequentially opening and closing said fluid operated valves in response to pressure fluid acting on said piston means, the duration of said cycles being substantially independent of the fluid pressure of said source.

~ .

~ i~76921 --3- Brief Description_of Draw~ Fig. l is a schematic side elevation view with a quarter section removed, showing a timer and sequencer device in accordance with a preferred embodiment of the invention.

Fig. 2 is a schematic perspective view showing the timer and sequencer device of Fig. 1 installed in a quick exhaust valve and manifold assembly for a dust collector application.

, Fig. 3 is a schematic side elevational view showing a typical dust collector apparatus in which the assembly of Fig. 2 may be installed.

Fig. 4 is a schematic block diagram to aid in the explanation and understanding of the operation of the pneumatic timer and sequencer apparatus of the invention.

Figs. 5 and 6 are graphs to aid in the explanation and understanding of the pneumatic timer and sequencer apparatus of the invention.

Descr~tion of Preferr'e'd Embo'diment , An application in which the pneumatic timer and sequencer apparatus of the invention is particularly useful is in dust collector systems, as for example, the dust collector system , for a blast hole drilling operation in the mining industry.

A typical dust collector for such a system is shown schematically by Fig. 3.

Dust-laden air is drawn from a shro,ud (not shown) surrounding the hole being drilled by the fan 11 which is mounted at the top of the dust collector cabinet 13.

The dust-laden air passes via the inlet conduit 15 into the dust collecto~ cabinet 13.

All of the air entering the cabinet 13 must then pass through filter elements 17. A typical dust collector may have from four to eight filter elements.

The one shown in ~ig. 3 has six filter elements.

The air passing through the filter elements 17 enters the upper compartment 19 of the cabinet 13 as cleaned air and is ~1769;~1 exhausted to the atmosphere via the fan 11 and outlet conduit 21.

In such an arrangement, the filter elements 17 would quickly become plugged with dust if suitable provisions were not made to prevent excessive dust accumulation.

One method for cleaning accumulated dust from a filter element 17 is to introduce a momentary flow of compressed air into the filter element outlet 23 thereby momentarily reversing the air flow through the filter element.

If the momentary flow of compressed air has sufficient energy, the accumulated dust in and on the filter element is blown loose and falls into the lower cabinet compartment 25 beneath the filter elements 17.

The dust that is blown loose is not picked back up into the air stream because of the very low air velocity in the lower cabinet compartment 25 and the compaction of the dust particles that occurred on the surface of the filter element. A flexible dump flap 27 is held in closed position during operation of the fan 11 but opens when the fan 11 is stopped at intervals when the drilling operation is suspended, thus allowing accumulated dust to dump into an appropr;ate receiver (not shown).

An inclined surface 29 forms the bottom of the lower cabinet compartment 25 so that gravity action will dump the accumulated dust.

Since it is desirable to maintain as nearly as possible a constant air flow through the dust collector, the filter elements 17 must be cleaned one-at-a-time in a repeated sequence.

The filter cleaner assembly 31 is mounted within the dust collector cabinet upper compartment 19 and is best shown in Fig. 2 as comprising an air pressure regulator 33, a mounting panel 3~, a manifold 37, a plurality of quick exhaust valves 39, and a timer and sequencer device 41.

It is desirable that the air cleaner assembly 31 should utilize the compressed air supply normally available from the drilling machinery at the site of operation, both to ~ il76921 supply the energy for the filter cleaning air flow and to operate the timer and sequencer device.

The compressed air from such supply (not shown) is connected to the regulator inlet 43, and the regulator outlet 45 is connected via conduit 47 to the timer and sequencer inlet 49, and from the timer and sequencer outlet 51 via conduit 53 to the manifold inlet (not shown).

The manifold 37 comprises a cylindrical body portion 55 and a plurality of outlets 57. A quick.exhaust valve 39 is mounted to each outlet.

There is a quick exhaust valve 39 for each filter element 17 (six in the embodiment shown).

The manifold outlets 57 are arranged in spaced parallel pairs, with the outlets of each pair being on opposite sides of the cylindrical body portion 55 and extending transversely of the cylindrical body portion.

The outlets 57 are dimensioned and disposed so that when the respective quick exhaust valve 39 is mounted, its exhaust outlet 59 will be a short distance above and centered on the respective filter element outlet 23.

The quick exhaust valves 39 are actuated to discharge a cleaning flow of compressed air by an air bleeding action.

Each quick exhaust valve 39 is connected via a respective air bleed conduit 61 to a respective poppet valve 63 which is connected on the poppet end closure 65 of the timer and sequencer device 41.

The timer and sequencer device 41 is mounted and fixed by suitable means (straps 67 and brackets 69) to the manifold cylindrical body portion 55.

A timer and sequencer device 41 in accordance with a preferred embodiment of the invention is shown by Fig. 1.

The timer and sequencer device 41 comprise,s an inlet end closure 71, a timer portion housing 73, a sequencer portion housing 75, and poppet end closure 65.

The timer portion housing 73 and the sequencer portion housing 75 are generally cylindrical and are joined by mating threaded portions 77.

The inlet end closure 71 and the poppet end closure 65 are 11769Zl I --6- fixed respectively to the outer ends of the timer portion housing 73 and the sequencer portion housing 75 by means of cap screws 79. Suitable seals 81 are provided to prevent air escape from the timer and sequencer device interior at these joints.

The timer portion housing 73 has a first cylindrical bore 83 adjacent threaded portion 77 which merges with a second and smaller~(than the first) cylindrical bore 85 which in turn merges with a third and larger (than the second) cylindrical bore 87 which opens to the inlet end of the timer portion housing 73.

The first cylindrical bore 83 sealingly receives the flange portion 89 of a piston rod guide 91 which has a hub portion 93 that sealingly receives the rod portion of a piston 97.

The flange portion 89 is clamped between the shoulder that is intermediate the first and second cylindrical bores 83, 85 and the inner extremity of the sequencer portion housing 75.

The piston 97 has a head portion 99 that sealingly engages and is reciprocable within the second cylindrical bore 85.

i ~ spool member 101 has a first flange portion 103 that .sealingly engages the outer end portion of the second cylindrical bore 85 and a second flange portion 105 that sealingly engages a third cylindrical bore 87.

The spool member 101 is clamped at its second flange 105 between a shoulder intermediate the second and third cylindrical bores 85, 87 and the inner surface of the inlet end closure 71.

Compressed air from the regulator 33 may be admitted at the timer and sequencer inlet 49 to a space 107 formed by a recess in the inlet end closure 71.

The space 107 communicates via a passage 109 in the timer portion housing 73 and a slot 111 in the hub portion exterior of the piston rod guide 91 to the space 108 on the rod side of piston 97.

The space 107 also communicates via an orifice OA in the spool member second flange portion 105 to the space 113 between the spool first and second flange portions 103, lOS and from there via timer and sequencer outlet 51 and conduit 53 to -7 the interior ~Vl) of the manifold 37.

The space 113 also communicates via-an orifice OB in the spool member first flange portion 103 to the space (V2) between the first flange poxtion 103 and the blind side of piston head portion 91.

The sequencer housing portion 75 has a cylindrical bore 115 which matingly receives a cylindrical sequencer cam or barrel 117 for reciprocation therein.

The sequencer cam 117 is journalled for *ee rotation about a bearing and retainer shaft 119 the inner end of which threadedly engages the outer end portion of the piston rod portion 95.

The sequencer cam 117 has a peripheral slot configuration 121 that provides a number of cam stations equal to the number of filter elements 17, and quick exhaust valves 39 that are being utilized in the dust collector system. A cam follower 123 is threadedly fixed to the sequencer portion housing 75 sidewall and engages the slot configuration 121.

Each stroke of the piston 97 of course provides a stroke o~ the sequencer cam 117, and each stroke of the sequencer cam 117 causes it to be rotated from one cam station to the next. A poppet valve actuator 125 is fixed to the outer end of the sequencer cam 117 and protrudes outwardly therefrom.

Every time the sequencer cam 117 approaches the~extremity of its stroke, the poppet actuator 125 engages a poppet valve and forces it to open so as to cause air to be bled from a corresponding quick exhaust valve 39, thus causing that quick exhaust valve to momentarily open to emit a cleaning flow of compressed air.

Thus, repeated reciprocation of the piston 97 will cause repeated stroking of the sequencer cam 117 which in turn will cause the poppet valves 63 and hence the quick exhaust valves 39 to be actuated in a repeated sequence.

The air that is bled by the poppet valves 63 is exhausted to the atmosphere via a passage in the poppet end closure 65, a fitting 127 and a conduit 129.

The timer portion housing 73 has an outlet 131 which communicates with the space or volume Vl and also via a conduit 133 to a reset valve 135 which is located on the front of the mounting -8- 11769Zl panel 35.

The reset valve 135 functions to dump air from the blind end of the piston 97 (V2) and force the completion of the retracting stroke in the event that the piston should fail to complete its retracting stroke in the normal manner.

The operation of the timer portion of the timer and sequencer device 41 may be explained with reference to the schematic block diagram of Fig. 4 and the graphs of Figs. 5 and 6.

It should of course be understood that the pneumatic timer of the invention may be utilized in various applications, and the timed strokes of the piston 97 may be utilized to perform any desired function.

In the preferred embodiment herein described, these timed strokes of piston 97 are used to actuate the sequencer portion of the timer and sequencer device 41.

In Fig. 4, the action of the sequencer is represented simply as a mechanical linkage 137.

Also, in Fig. 4 there is for simplicity shown only a single poppet 63 and a single quick exhaust valve 39.

Compressed air from a suitable source, such as the source normally available at an operations site to serve various functions, is fed via a conduit 151 to the inlet 43 of regulator 33.

The regulated air from the regulator outlet 45 is fed via conduits 139, 141 to the space or volume on the rod side of piston 97, and via conduits 139, 143 to orifice A.

Air from orifice A is fed via conduits 145, 147 to manifold 37 (Vl, and via conduits 145, 149 to orifice B.

The manifold 37 is connected via conduit 153 to quick exhaust valve 39.

Air is fed from orifice B to the space or volume (V2) on the blind side of the piston 97.

Assume that the quick exhaust valve 39 has been actuated to emit a cleaning flow of air (at time zero in Fig. 6), so that the pressure in the manifold 37 (Vl) drops rapidly to a low value (near atmospheric pressure).

Because the air supply from regulator 33 must pass through orifice A the pressure in manifold 37 builds back-up to its maximum value during a time interval shown by Fig. 6 as a little less than four seconds.

During the first portion (about one second) `-~" 117~i921 g of this time interval the V2 pressure drops as air moves out of V2 via oriice B toward Vl. ~hen the V2 pressure has dropped to a value such that the pressure V2 times the piston blind end area is less than the regulated pressure times the piston rod end area, the piston 97 begins its retracting stroke.

The piston 97 then retracts at a substantially constant rate until it reaches the end of its retracting stroke.

The piston retracting stroke takes a time interval of about one second.

During the piston retracting stroke, the V2 pressure remains substantially constant because of the relationship between the decreasing V2 volume and the rate of air flow through orifice B.

When the piston reaches the end of its retracting stroke, the volume V2 becomes constant and so the V2 pressure drops until the Vl pressure builds sufficiently to reverse the air flow through orifice B at which time the V2 pressure begins to rise.

Then the V2 pressure continues to rise until the V2 pressure times the piston blind end area exceeds the regulated pressure times the piston rod end area at which time the piston 97 begins its extending stroke (at about time two seconds in Fig. 6).

The piston 97 extends at a substantially constant rate until it reaches the end of its extending stroke (at about time four sec~nds in ~ig. 6).

During the piston 97 extending stroke the V2 pressure remains substantially constant because of the relationship between the increasing ~2 volume and the rate of air flow through orifice B.

When the piston 97 reache$ the end of its extending stroke the volume V2 becomes constant and so the V2 pressure increases until the next quick exhaust valve 39 in the sequence has been fired and then decreases until the piston 97 again begins its retracting stroke at which time the V2 pressure again becomes constant.

An important feature of the present invention is that the pneumatic timer cycle time is substantially constant -over a wide range of air supply pressures.

As can be seen il769Z~ I -10from Fig. 6, the time fo~ one cycle of the timer i9 made up of (1) the time of dwell of the piston at the extended stroke end, (2) the time of piston travel during the piston retracting stroke, (3) the time of dwell of the piston at the retracted stroke end, and (4) the time of piston travel during the piston extending stroke.

The dwell times of (1) and (3) above depend on the ratio of the rod end to blind end areas of the piston 97, the sizes of orifice A and orifice B, and the volume (Vl) of manifold 37, all of which are constant.

Consequently, these dwell times are entirely independent of air supply pressure.

The piston travel times of (2) and (4) above are constant because the applied forces are constant.

The applied forces are the piston rod end pressure (which is the same as the air supply pressure and can be considered as constant for the brief period of a given timer cycle) times the piston rod end area (which of course is constant) and the V2 pressure (which is constant during the piston travel times ~as hereinabove explained) times the piston blind end area (which is of course a constant).

It is thus apparent that the piston travel times aré independent of air supply pressure.

Since both the dwell times (1) and (3) above and the piston travel times (2) and (4) above are independent of air supply pressure, it follows that the pneumatic timer cycle time is independent of air supply pressure, and can be said to be substantially constant at least over a wide range of air supply pressures.

Another feature of the present invention is that the pneumatic timer has relatively few working parts and can be ruggedly constructed so that it is highly reliable in operation even in hostile environments and also is suscep tible to normally available field maintenance.

It is understood that the graphs of Figs. 5 and 6 are generalized for illustration purposes and were not drawn from actual data.

Curve A of Fig. 5 simply illustrates , . . .

-` :1176921 that the pneumatic timers of the prior art of which I am aware have cycle times that vary considerably with variations in air supply pressure, whereas curve B of Fig. 5 illustrates that the cycle time of the pneumatic timer of the present invention is substantially constant over a wide range of air supply pressures.

The foregoing disclosure and the showings made in the drawings are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense.

;. .